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Underwater Transect

New Zealand extends through a wide range of latitudes—from semi-tropical waters off the Kermadec Islands in the north, to frigid, tempestuous seas that lash subantarctic islands in the south. Here, unique marine organisms inhabit an equally strange underwater terrain, a product of the volcanism that accompanies seafloor subduction to form ridges, reefs, pinnacles and a […]

Issue 198

Mar - Apr 2026

Black-Backed Gulls
Meth & HIV in Fiji
Dung beetles
Centro
Rogaining

Subscribe
Issue 198 Mar - Apr 2026

Gull spotting

For shame

When black-backs attack

Two years on Mana Island

Before the flood

A delicious crayfish circle of life

Bay of Islands: Putahataha Island in the Bay of Islands is one of the few dive spots in this area where the boulders are not covered in Ecklonia kelp. At a depth of around 10 metres, a large cave—its entrance fringed with colourful soft corals, anemones and sea urchins—is internally lit by reflections off the white sand bottom. A favourite haunt of short-tailed stingrays, pigfish, moray eels and hiwihiwi, the sculpted cave walls lead to an undulating ceiling where thousands of bigeyes congregate.
Cavalli Islands: The most infamous of wrecks, the Rainbow Warrior was scuttled southwest of Motutapere Island in 1987 after its scandalous bombing by French agents. Reconstituted as a reef, it wears a rich invertebrate carpet (far left). Neptune’s Garden (left), between Tuturuowae and Nukutaunga islands, abounds with eagle rays, sponges, invertebrates, crayfish and kelp.
Cavalli Islands: The most infamous of wrecks, the Rainbow Warrior was scuttled southwest of Motutapere Island in 1987 after its scandalous bombing by French agents. Reconstituted as a reef, it wears a rich invertebrate carpet (far left). Neptune’s Garden (left), between Tuturuowae and Nukutaunga islands, abounds with eagle rays, sponges, invertebrates, crayfish and kelp.
Great Barrier Island: Perfectly poised to take advantage of passing currents, the Twin Peaks—pinnacles rising from the sea floor 300–400 m north of Motuhaku Island near Port Fitzroy—are the location of an extraordinarily diverse biomass: anemones, finger and golf ball sponges, orange soft corals, and numerous fish species including kingfish, boarfish, mado, bigeyes, golden snapper, porae, butterfly perch and damoiselles that hover near the ledges, overhangs and archways.
Aldermans: Ruamahua-nui, the Spire, Ruamahua-iti and Hongiora islands are the remnants of a large volcano that make up the Alderman Islands, 12 km east of the Coromandel coast. Its footings honeycombed by a collection of caves and wide connecting corridors, Hongiora Island is a dive site to explore and savour. Of the four caves, the largest—visible above water—can be entered and navigated by kayak. Beneath the surface in this hidden labyrinth, afternoon sun caps the ends of tunnels with a spectral blue light, and encrusted rock walls blaze orange and yellow under torch light.
White Island: White Island is a large, partially submerged volcano with only 320 of its 1600 metres above sea level. The Diadema Reef straddles a steep-sided submerged pinnacle nearby, which is topped with kelp. Various sea urchins dwell here including, at 20 m, the red spined Diadema palmeri (left, for which the reef is named). The urchin’s prominent ‘eyeball’ is actually its anal sac, connected to a toothed mouth under its body.
Marlborough Sounds: Cape Jackson, protruding from the mouth of Queen Charlotte Sound, has forests of giant kelp (Macrocystis pyrifera) where seahorses, blue cod, large butterfish and blue moki weave and flutter around rubbery limbs and holdfasts. Such forests are a feature of the area, and when the sun penetrates gaps between the leaves, the dazzling lightshow is simply magical. It is also the location of New Zealand’s largest shipwreck, the Mikhail Lermontov, a luxury Russian passenger liner that sank in 1986—its hull ripped apart as the pilot manoevred the 150 m, 20,000 t vessel through the narrow passage.
South Wellington: The attractive and at times tumultuous waters of Owhiro Bay on Wellington’s rocky south coast have claimed various craft, including a 153 ft wooden sailing ship, a three-masted barque, an iron steamer and a Japanese fishing trawler. It was recently designated a marine reserve (Tuputeranga Marine Reserve), to protect the prolific life thriving in the type of rich seas that only a steady, replenishing current can provide. A school of yellow-eyed mullets (centre) and filter feeding brittlestars (bottom), take advantage of this abundant food supply.
Milford Sound: A vertical, seemingly never-ending wall plummets into unseen depths in Greenstone Bay on the southern side of Milford Sound, where a surface layer of water stained dark with tannins encourages various deepwater organisms to live near the surface. These include large black coral trees, gorgonian fans and brachiopods—living fossils that are virtually unchanged from those that appeared 500 million years ago in the early Cambrian and are normally only found in the deep polar regions of the world. A red hydracoral (Errina novaezelandiae), this one found in a sand pocket at 16 m on a rocky ledge of Greenstone Bay, looks like a good place to forage to a hungry gastropod. The fiord is 16 km long and connects to the Tasman Sea at St Anne Point, where girdled and scarlet wrasse abound.
Otago: The Aramoana Mole is New Zealand’s first man-made reef, near Otago Harbour. A giant structure built with prison labour, the Mole has shielded the harbour entrance for more than a century. Numerous ships have been scuttled along its length, including Paloona.
Stewart Island: Northeast of Halfmoon Bay on Stewart Island are the Titi/Muttonbird Islands which include the Bunker Islets, prime real estate for a seal colony. Cumbersome on land, seals are playful and curious in water and more than prepared to show off their mesmerising agility to any divers that venture into their element.

New Zealand extends through a wide range of latitudes—from semi-tropical waters off the Kermadec Islands in the north, to frigid, tempestuous seas that lash subantarctic islands in the south. Here, unique marine organisms inhabit an equally strange underwater terrain, a product of the volcanism that accompanies seafloor subduction to form ridges, reefs, pinnacles and a network of large underwater canyons and trenches.

(more…)

Issue 198

Mar - Apr 2026

Black-Backed Gulls
Meth & HIV in Fiji
Dung beetles
Centro
Rogaining

Subscribe
Issue 198 Mar - Apr 2026

Gull spotting

For shame

When black-backs attack

Two years on Mana Island

Before the flood

A delicious crayfish circle of life

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